The determination of the altitude of bodies above the surface of the earth has interested physicists, meteorologists, balloonists, mountain climbers, and aviators. The methods used have been similar and rest on facts which have been well known for a long time. This paper is confined to the theory and methods of the accurate determination of altitude of aircraft above the earth’s surface and brings together all of the well known facts and methods in addition to some new material.
It is here emphasized that for aviation purposes, the altitude is determined by observations of pressure and temperature. A relation of pressure and temperature to altitude is derived. This expression is:
in which h is the altitude in feet, P0 is the atmospheric pressure at the ground level, P is the pressure at the upper level, and tm is the mean temperature of vertical column of air between the two levels.
A more complete expression for the altitude is also derived in which the factors of slight practical importance are included. These factors are those of humidity and gravity.
The observations of pressure and temperature necessary to determine an altitude are discussed. The instruments used to make these observations are briefly described.
The method of computation of the altitude from these observations is outlined and illustrated by a sample computation.
The paper concludes with tables of upper air data, aircraft performance standards and altimeter calibration standards for the United States and other countries.
© 1923 Optical Society of AmericaFull Article | PDF Article